The present invention relates to packet-switched networks, such as Internet Protocol (IP) networks. More particularly, the present invention relates to a method, computer program and apparatus for allowing hand-off of an endpoint in a packet-switched network by allowing the relocation of a gatekeeper during a call when the endpoint moves to a different zone of the packet-switched network.
Voice or telephony services can now be provided over a packet-switched network, such as the Internet. These packet-switched networks are commonly referred to as IP networks, IP telephony networks or Voice over IP (VoIP) networks because the Internet protocol according to various IP based standards is the primary protocol used. One such IP based standard, for example, is the International Telecommunication Union (ITU) H.323 Standard.
The H.323 Standard provides a foundation for audio, video, and data communications across IP networks. By complying with the H.323 Standard, multimedia products and applications from multiple vendors can interoperate, allowing users to communicate without concern for compatibility. The H.323 Standard is part of a larger series of communications standards that enable audio video conferencing across a range of networks.
The H.323 standard defines four major components for a network based communications, namely terminals, gateways, gatekeepers and Multipoint Control Units (MCU).
Terminals are the client endpoints on the network that provide realtime two-way communications. All terminals which comply with the H.323 standard must also support the ITU H.245 standard, which is used to negotiate channel usage and capabilities. Further, terminals which comply with the H.323 standard are required to implement the ITU Q.931 and the H.225 standards for call signaling and call setup, including for Registration/Admission/Status (RAS) processing. Optional capabilities in terminals which comply with the H.323 standard are MCU capabilities.
The gateway is an optional element when implementing the H.323 standard. Each gateway provides many services the most common being a translation function between the H.323 standard conferencing endpoints and other terminal types. For example, this function could include translation between transmission formats and between communication procedures.
Gatekeepers are the most important component of an H.323 standard enabled network. It acts as a central point for all calls or communication within a zone serviced by the gatekeeper and provides call communication control services to registered endpoints. The gatekeeper could be considered a virtual switch. The gatekeeper performs four important call or communication control functions. The first is address translation from, for example, aliases for terminals and gateways to transport addresses. The second is admission control where the gatekeeper authorizes network access based on call authorization, bandwidth, or some other criteria. The third is bandwidth control which provides bandwidth management wherein the gatekeeper if necessary can refuse to make connections. The fourth is zone management where the gatekeeper provides each of the above noted functions for the terminals, MCU""s,and gateways that have been registered in the zone serviced by the gatekeeper.
The MCU supports conferences between three or more endpoints. Under the H.323 standard an MCU includes a multipoint controller which handles H.245 standard negotiations between all terminals to determine common capabilities for audio and video processing, and possibly a multipoint processor which mixes, switches and processes audio, video and/or data bits.
Each of the above described endpoints, gateway, gatekeeper, and MCU can be implemented by use of apparatus such as a personal computer (PC), workstation, server, etc.
The above described H.323 standard as defined is intended to operate in fixed packet-switched networks where the endpoints, for example, terminals such as workstations, PC""s, etc., that conform to the H.323 standard, do not move to a new zone serviced by another gatekeeper. As illustrated in FIG. 1, a packet-switched network which implements the H.323 standard can, for example, be organized into a plurality of zones 100a-n. Each zone 100, for example, could include a plurality of terminals 10a-n, a gatekeeper 12, at least one gateway 14, at least one router 16 and at least one MCU 18. Each of the routers 16a-n included in the packet-switched network interconnects, for example, sub-networks included in a zone 100 to each other, or interconnects, for example, zones of the packet-switched network included in different zones of the packet-switched network 100a-n to each other.
The packet-switched network illustrated in FIG. 1 implementing current IP standards, including the H.323 standard does not allow for the roaming or mobility of the endpoint during a call or communication. Thus, for example, the terminals 10a-e cannot roam or be mobile among the zones 100a-n in the packet-switched network while a call or communication is being conducted. For example, such roaming or mobility is important if, for example, the endpoint (terminal) is implemented by a mobile telephone, laptop, Personal Communications Services (PCS) device, etc., which comply with the H.323 standard.
Therefore, there exists a need for a technique that allows endpoints implementing the H.323 standard to be able to roam or have mobility between different zones, networks or sub-networks of a packet-switched network.
The present invention provides a method, computer program and apparatus for allowing hand-off of an endpoint in a packet-switched network enabled by the H.323 standard by allowing the relocation of a gatekeeper during a call when the endpoint moves to a different section of the packet-switched network.
Particularly, the present invention provides a technique of allowing endpoints to move between different zones of a packet-switched network while maintaining communications already established with another endpoint. The present invention accomplishes this by establishing a communication between local and remote endpoints via a first gatekeeper, which services a first zone of the packet-switched network, when the local endpoint is at a location serviced by the first zone of the packet-switched network. The local endpoint is mobile and can be, for example, a device such as a wireless telephone, laptop computer, PCS device, etc. When the local endpoint moves to a location serviced by a second zone of the packet-switched network, the communication is maintained between the local and remote endpoints via the first and second gatekeepers. The second zone of the packet-switched network is serviced by the second gatekeeper.
The communication between the local and remote endpoints via the first and second gatekeepers is maintained by causing communication control functions previously performed by the first gatekeeper to be handed-off to the second gatekeeper. After such initial hand-off, the first gatekeeper relays communications between the remote endpoint and the second gatekeeper, and the second gatekeeper relays communications between the first gatekeeper and the local endpoint and performs communication control functions on communications between the local and remote endpoints. Thus, the present invention provides that when the local endpoint moves to a location serviced by a second gatekeeper, and after an initial hand-off the first gatekeeper performs primarily a relaying function and the second gatekeeper performs a relaying function and communication control functions between the local and remote endpoints.
The present invention also provides a technique for maintaining communication between the local and remote endpoints when the local endpoint moves, subsequent to the above described move, to a location serviced by a third zone of the packet-switched network. The third zone of the packet-switched network is serviced by a third gatekeeper. Communication between the local and remote endpoints is maintained by causing communication control functions previously performed by the second gatekeeper to be handed-off to the third gatekeeper. After such subsequent hand-off, the first gatekeeper relays communications between the remote endpoint and the third gatekeeper, rather than the second gatekeeper, and the third gatekeeper relays communications between the first gatekeeper and the local endpoint and performs communication control functions on communications between the local and remote endpoints. Thus, the present invention provides that when the local endpoint moves, subsequent to the above describe move, to a location serviced by a third gatekeeper, and after a subsequent hand-off, the first gatekeeper performs primarily a relaying function and the third gatekeeper performs a relaying function and communication control functions between the local and remote endpoints.
In the present invention, the above described technique for maintaining communication between the local and remote endpoint when the local endpoint moves, subsequent to an initial move, to a location serviced by a third zone of the packet-switched network can be applied to any further subsequent moves of the local endpoint to a location serviced by a further zone of the packet-switched network. The further zone of the packet-switched network is serviced by a further gatekeeper. Communication between the local and remote endpoints is maintained by causing the communication control functions previously performed by the third gatekeeper to be hand-off to the further gatekeeper. After such further subsequent hand-off, the first gatekeeper relays communications between the remote endpoint and the further gatekeeper, rather than the third gatekeeper. The further gatekeeper relays communications between the first gatekeeper and the local endpoint and performs communication control functions on communications between the local and remote endpoints.